Electric switch



Patented Oct. 30, 1928.

UNITED STATES 1,689,495 PATENT oFFlcE.

FRANK MCELBOY, 0F MANCHESTER, ENGLAND, ASSIGNOR TO J. H. TUCKER COM- I PANY, LIMITED, 0F BIRMINGHAM, ENGLAND.

ELECTRIC SWITCH.

Application led August 9, 1926, Serial No. 128,307, and in Great Britain November 8, 1925.

This invention has reference to improvements in electric switches of the type which are known as plug switches, that is, a switch and socket combined on one base and associated with an appropriate plug, which members may be interlocked or operated by the lug. i

T e invention has among its objects the construction of a double-pole plug switch which shall be completely elicient in its operation, will avoid arcing, and cannot be operated or tampered with by an unauthorized person, 'the mechanism being so arranged that the switch cannot be put out of operation or made ineffective through misuse, as obtains in connection with certain known forms of plug switch, a feature of the invention residmg in so constructing and arranging the mechanism that the apertures in the plug socket or base do not give direct access to the contact arms or any normally live part of the switch when the switch is in the oi position, so asto avoid the possi-l bility of. a misuse or tampering with the switch mechanism. A `further feature of the invention resides in the provision of an automatic spring-controlled quick make-andbrea-k operation of the switch mechanism which is set in operation by the insertion or withdrawal of the plug of the switch irrespective of the s eed at which the plug is inserted or lwith rawn from the socket or base, so that an effective break of the circuit is ensured even without effecting a complete withdrawal of the plug to avoid the possibility o any arcing.-

It should be appreciated that a switch of this type may be combined with means for independently operating the switch, distinct from the plu that is, a switch control may be introduce -in the form of a tumbler or dolly-operated mechanism which can be employed to effect an independent` control of the switch circuit additional or alternative to that ei'ected by means of the plug.

This invention consists of an electric switch of the plug type hereinbefore referred to, wherein the plug pins constitute removable contacts of the switch, the switch mechanism being so arranged that the withdrawal of the plu removes the circuit completing members o the switch from the path of the plug pins. The invention further resides in mounting on the plu'g means whereby withdrawal of the plug effects a positive break which (as distinct from a spring-effected break) between the contact arms and the fixed contacts of a multi-pole switch. Further, the mechanism is so arranged that the moving switch arm or arms make contact on the one hand with fixed terminals, and on-the other hand with terminals constituted by the removable plug pins, the switch arms belng so mounted and arranged that they are removed from the path of the plug pins on the withdrawal of the plug. Further, the

mechanism is so arranged and constructed that 1n the event of the spring failing to act to eect the quickmake-and-break operation the switch circuit can be positively made and boken by the insertion or withdrawal of the p ug.

Inorder that this invention may be clearly understood and readily carried into practice, reference may be had to the appended explanatory ..sheet of drawings, upon plan.; view of switch mecha-y according to the present particularly a plug and its plug pins or contacts and slotted casing for the switch mechnism. Describing now, broadly, one means of carrying the present invention into eect as embodied in a plug switch which has not provision for independent operation, the base part of the switch is constructed inthe form of a disc a1 with projections a1, upon which disc the switch mechanism proper is mounted. The cover?) of this box is of cylindrical or inverted cu formation and is formed with three smal rectangular apertures b1 b2 b3 therethrough whereby the blades or arms k1 k2 ha which are secured to the plug k can be inserted into-the box b and make contact with the switch mechanism contained therein, the said blades or arms being mounted on an insulated cap or head in known manner.

The switch mechanism upon the base a comprises a pair of xed contacts c secured to the projections a1 and having terminals c1, which contacts are adapted to be engaged by a pair of switch contact arms d when the switch mechanism is in the circuit-closing position. The contact arms are mounted upon, but insulated from, a spindle e sup! ported by the projections al, and secured to this spindle is a jawed member f which serves to ensure by its co-operation with the arm k2 of the plug the rotation of the said spindle e. Pivotally connected to this jawed member f is the spindle g of the springcontrolled toggle-operating mechanism forv efecting the quick make-and-break action of the switch, the spindle being surrounded by a coiled spring g1 functioning in compression, the said spring abutting at the one end against a collar or shoulder g2 formed on the said spindle, and at the other end against a roller g3 which is freely mounted on a pin which in turn is mounted on a pivotally mounted segment z, which will be hereinafter described, the said roller having a passage therethrough for the free end of the said spindle g, whereby the desired compression and extension of the coil spring g1 may be effected in known manner. The pivotally mounted segment h to which reference has just been made is mounted on a pin h1 carried by a U-shaped bracket z', and is slotted at h2 to permit of the free passage therethrough of the main spindle e of the switch on which the contact arms d are fixed, the segment being extended by means of projections h3 it* which co-operate with the arm k2 of the plug for the purpose of effecting the operation of the switch on the insertion or withdrawal of the plug, as will be hereinafter more particularly described, the projections h3 taking the form of a pair of lugs extending from the periphery of the segment having a pair of cam surfaces h? also extending from the periphery of the segment and adapted for use in co-operation with the lugs hereinbefore referred' to.

Mounted on the said'segment are a pair of rollers 7' adapted to co-operate with the jawed member f hereinbefore referred to for the purpose of ensuring that only a correct operation or functioning of the switch mechanism can obtain, that' is, tampering or unauthorized operation of the switch mechanism is prevented, the said pair of rollers j also providing a lost motion con-- nection between the segment b and the spindle c on which the contactarms d are mounted.

The plug of the switch comprises an insulatedcap or .head 7c from which project the three arms or blades k1 7a2 k3 two of the said arms or blades 101 7c3 constituting removable lContact of the switch, and the other arm or mechanism within the box and constitutingA the positive operating element of the switch and earthing pin of the plug. The slot 7a4 in the arm or'blade k2 is sha ed to admit, firstly, of the engagement o the slotted arm with the cam surfaces lz?, the cam surfaces directing the slotted arm of the plug of the switch after insertion within the socket or base into engagement with the lugs ha also extending from the periphery of the segment. The further insertion of the plug into the box constituting the base of the switch causes the slotted arm or blade to depress the segment l. and rotate it about its pivot bl until the compression spring mechanism g1 is moved across the dead centre when the spring functions to effect aquick make action of the Contact arms of the switch. Ineffecting this operation, the lower of the two jaws of the member f hereinbefore referred to is borne upon by the innei' end of the slotted arm 702 and the other jaw of the said member passes'through the slot cin this arm and serves to retain the plug in position within the socket or base of the switch while the switch is closed. A withdrawal of the plug 7c first of all effects an engagementof the slotted arm 7c? with the lugs It* on the periphery of the pivoted segment h, and subsequently with the upper .jaw of the member f mounted 'on the spindle e carrying the contact arms d, whereby the segment is returned to its initial position,

ythe coil spring y again operating after it has passed the dead centre position to effect a quick break, in that it removes the contact arms d rapidly from the fixed Contacts c irrespective of the speed at which the plug 'k is withdrawn from the base.

The two rollers j which co-operate respec tively with the two jaws of the jawed member f form the means of connection between the pivoted segment 71, and the spindle e on which the contact arms d are mounted, and permit of a lost motion obtaining between the said segment and the said spindle.

The contact arms d mounted on the said spindle e are preferably as shown each in the form of double blades adapted to engage on either side of the fixed contacts c, and of the plug contact arms or blades cl k3 which form the removable contacts of the switch, thereby ensuring an effective and complete circuit through the four terminals of the switch,

two of the terminals associated with k1 los being removable with the plug, and the other two cl being associated with theixed contacts o mounted on theA base of the switch.

The jawed memb'er f which co-operates with the slotted arm k2 of the plug, in addition to constituting part of the lostv motion mechanism of the switch, also serves to pre vent misuse or tampering with the`switch mechanism in that the insertion of a solid blade in place of the slotted arm would not effect an loperation of the switch mechanism,

as it would be fouled by the jaw of the said I member subsequent to insertion and thereby prevent a complete insertion, and so prevent the switch circuit fromv being closed accidentally or by an unauthorized person.

As hereinbefore mentioned, an independent switch circuit control may be embodied in the switch-whereb even assuming the plug to be inserted t ie circuit may be broken.

What I claim as m invention and desire to secure by Letters atent lisz-f- 1. In an electric switch of the plug type, plug -pins constituting removable contacts of the switch, circuit vcompleting means comprising members movable into and out of the path of movement of the plug pins, and means whereby withdrawal of the plug removes the circuit completing means of the switch from the path of the plug pins.

2. In the structure of claim 1, said circuit completing means including a multiple switch comprising movable contact -arms and fixed contacts, and mechanism whereby withdrawal of the plug pins effects a positive break between the contact arms and the fixed contacts of the multi-pole switch.

3. In an electric switch of the plug type, a removable plug, plug pins, switch mechanism comprising an arm adapted to make contact on the one side with a fixed terminal and on the other side with a terminal constituted by a pin on the removable'plug, said switch arm being removable from the path of the plug pin and the fixed terminal and means where y removal of the plug removes the switch arm from the path of the plug pin and from the fixed terminal.

4. An electric switch according to claim 3, wherein the switch arm comprises spring means for affecting a quick make-and-break operationand means whereby the. switch arm or arms is positively actuated by the insertion or withdrawal of the plug on failure of the yspring means.

5. In an electric switch, switch mechanism provided with two fixed contacts, two pivotal contact arms, means for rotating said contact arms into and out of engagement with said contacts comprising a movable demember, an arcuate slot a apted to receive the spindle, a spring-controlled toggle linkage between the spindle and the segmental member, projections upon said segmental .1

member, fixed contacts adapted to be engaged by the contact arms, and a plug member comprising an arm havin a slot adapted to co-operate with the'projectlons on the segmental member and also with the jawed member, and two arms adapted to cooperate with the contact arms.

In witness whereof I have hereunto set' my hand.

FRANK MCELROY. v 

